/**
 * 最长回文子串
 * https://leetcode.cn/problems/longest-palindromic-substring/
 */
class Solution {
    public String longestPalindrome(String s) {
        int n = s.length();

        boolean[][] dp = new boolean[n][n];

        int begin = 0,len = 1;
        for(int i = n -1;i >= 0;i--){
            for(int j = i;j < n;j++){
                if(s.charAt(i) == s.charAt(j)){
                    dp[i][j] = i + 1 < j ? dp[i+1][j-1] : true;
                }
                if(dp[i][j] && j - i + 1 > len){
                    len = j - i + 1;
                    begin = i;
                }
            }
        }

        return s.substring(begin,len + begin);
    }
}